Brominated polymers from isobutylene and p-methylstyrene are disclosed in U.S. Pat. No. 5,162,445. The brominated polymers are high in isobutylene content and sometimes can be substituted for butyl rubber (including halogenated butyl rubber) in many applications including tire innerliners and tire curing bladders.
Sometimes it is desirable to decrease spider flow without sacrificing other properties of an uncured rubber composition. Spider flow relates to the tendency of the rubber composition to flow under heat and pressure during curing. Quantification of the spider flow starting uncured and finishing cured helps predict deformation of the rubber component during molding and curing of the green tire.
The spider flow test is a measure of the tendency of a rubber composition to flow over a time period, through a specified diameter orifice in a transfer type mold preheated to a specified temperature thereby filling a complex pattern in the mold. The amount of extrudate which passes through the orifice is weighed. A constant force from a hydraulic ram is used to force the rubber through the orifice. The mold uses a 35 gram uncured rubber sample. It is to be understood that the viscosity of the rubber is changing during the test because the uncured rubber is crosslinking to a cured state during the test. The name spider flow is used because the mold produces a specimen having a central plug and a multitude of appendages therefrom known as the legs. Examples of the molded specimen output are shown in The Vanderbilt Rubber Handbook 13th Ed. published by the R. T. Vanderbilt Company Norwalk, CT (1990) page 434, 454 and 464.